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Breakthrough in understanding gut infections

MARK COLVIN: A team of international researchers say they've discovered a crucial mechanism that defends the human gut from infections like E. coli.

They've found that bacteria switch off the body's ability to fight off the infection.

They're optimistic the discovery could eventually lead to the development of a vaccine.

It could also improve treatments for people with inflammatory bowel disease.

Samantha Donovan reports.

SAMANTHA DONOVAN: Nearly 30 scientists from Melbourne and overseas have been studying virulent forms of E. coli to try and understand how it takes hold in the human gut.

The report's lead author, Professor Elizabeth Hartland, is a microbiologist at the University of Melbourne.

ELIZABETH HARTLAND: What we've discovered is that when they infect the gut they're able to switch off an immune defence pathway that we have, which is designed to get rid of infected cells. This is interesting because this pathway is often defective in people with inflammatory bowel disease. So, the bacteria allowing us to investigate processes in inflammatory bowel disease that we didn't know about before.

SAMANTHA DONOVAN: Professor Hartland says about 5 million people around the world have inflammatory bowel disease while infections like E. coli can be fatal.

ELIZABETH HARTLAND: So they're a cause of diarrhoea in children mainly, especially in developing countries, but they can also cause a nasty kind of kidney failure in children and adults in industrialised countries. So they can be quite life-threatening infections and they're whole aim is to attach to our gut and not let go.

And as a counter defence to that we have a pathway, which is called programmed cell death, and that's designed to expel these infected cells and kill them. But the bacteria have got around this by specifically blocking this pathway using a chemical modification, and it's a very new one, it's not been recognised before. And so this has big implications for how we understand how infections occur, and also what this pathway does in defending our gut against infection and allowing our gut to function normally.

SAMANTHA DONOVAN: Does this bacteria only shutdown the body's ability to fight off E. coli or other infections as well?

ELIZABETH HARTLAND: The bacteria salmonella have a similar group of toxins that they're able to inject into the cell. We haven't studied those yet and so we don't know if they function in exactly the same way, but they're part of a larger group of toxins that intestinal bacteria pathogens we call them produce.

SAMANTHA DONOVAN: What then will this discovery enable you to do in terms of looking at possible treatments?

ELIZABETH HARTLAND: What it's allowing us to do is first of all understand how bacteria cause disease in much more molecular detail. But it's also given us a model to understand the processes in inflammatory bowel disease because we find that when animals and people are deficient in this pathway then they get much more inflammation in the gut and they get that inflammation for longer and there's much more tissue damage that occurs. So now we have a good model to be able to start to dissect those pathways and understand the basis of that disease in much greater detail, and hopefully then lead to better therapies for these inflammatory conditions.

SAMANTHA DONOVAN: What sort of treatments?

ELIZABETH HARTLAND: So, ultimately by understanding how the bacteria cause disease we hope to be able to develop vaccines for these kinds of organisms, and also other kinds of perhaps immune therapies and adjunct therapies to at least lessen the infection if not prevent the transmission of the infection from person to person.

SAMANTHA DONOVAN: The research has been published today in the journal Nature.